Unless otherwise indicated herein, the materials described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
A speaker is an electroacoustic transducer that converts an electrical signal into a corresponding sound. For human audibility, an ideal speaker or earphone should generate a constant sound pressure level from 20 Hz to 20 kHz. In other words, the ideal speaker should have a flat frequency response within the audible frequency range. Electromagnetic speakers, such as dynamic loudspeakers, typically include a diaphragm that is driven by a magnetic coil. Because the coil moves together with the diaphragm, the large total effective moving mass as well as the mechanical properties of the diaphragm and diaphragm suspension can cause poor high frequency response. This non-flat frequency response, along with negative effects of potential/kinetic energy stored by the large mass (e.g., the diaphragm may not start or stop motion immediately in response to the input electrical signal), can reduce the quality of the sound produced by the speaker.